Starving People vs Food Store: how to find good keyword

hello,
first, i am new here, my name is anest, i want to share about how i search keyword, this is my very simple method, and i am very happy if others can put other advice / critic / input so it will be more good (perfect?)

and yes you can get a market samurai or keyword elite to find a good keyword, but this is just simple and free method i do ..

and (still) yes, all purpose / aim of this IM things are to be NUMBER ONE (#1) in SERP, right

ok,
here i will explain variable first ->

A. search result on google (serp) with keyword that we search = competitor Food Store
B. global monthly search from Google Keyword Tool = Hungry People
C. page rank = popularity of competitor food store

and simple step ->
1. open google adword keyword tool (KWT)
2. put 2word main keyword
3. select using "exact"
4. see any high 3word keyword with high "global monthly search", save tht number, it is number of "hungry people" (example 100)
5. open google
5. put that 3word to google, click search (without "" and without intitle=)
6. save result number (example, 1.000), so this is number of "Food Store"
7. calculate ->
your-percent-opportunity-to-win = hungry people / food store
10% = 100 / 1.000

so your store have opportunity to visit by 10% or 10 "hungry person" (from 100 hungry person)

but,
it is too simple,
now you can check "popularity of competitor food store",

8. on 1st page of serp of google search (at step number 5), check the PageRank of every web on it (take 10web), and make average number
9. if average pagerank are upper then 2, maybe it is will lower "your-percent-opportunity-to-win" ..

so that's it simple method,
of course you can put more variable, more complex method / calculation .. and don't forget that every "food store" have their own "recipes" like SEO, backlink, email marketing, etc etc ..